Decline of Anti-SARS-CoV-2 IgG Antibody Levels 6 Months after Complete BNT162b2 Vaccination in Healthcare Workers to Levels Observed Following the First Vaccine Dose

Research on post-vaccination antibody dynamics has become pivotal in estimating COVID-19 vaccine efficacy. We studied anti-SARS-CoV-2 Spike RBD IgG levels in 587 healthcare workers (2038 sera) who completed BNT162b2 vaccination. Average antibody titer 3 weeks after the first dose in COVID-19-naïve participants (median 873.5 AU/mL) was 18-fold higher than the test threshold, with a significant increase 1 month (median 9927.2 AU/mL) and an exponential decrease 3 (median 2976.7 AU/mL) and 6 (median 966.0 AU/mL) months after complete vaccination. Participants with a history of COVID-19 prior to vaccination showed significantly higher antibody levels, particularly after the first dose (median 14,280.2 AU/mL), with a slight decline 1 month (median 12,700.0 AU/mL) and an exponential decline in antibody titers 3 (median 4831.0 AU/mL) and 6 (median 1465.2 AU/mL) months after vaccination. Antibody levels of COVID-19-naïve subjects after the first dose were moderately correlated with age (r = −0.4). Multivariate analysis showed a strong independent correlation between IgG levels 6 months after vaccination and both IgG titers after the first dose and 1 month after vaccination (R² = 0.709). Regardless of pre-vaccination COVID-19 history, IgG levels 6 months after vaccination were comparable to antibody levels reached by COVID-19-naïve participants after the first vaccine dose.

Topical medication as an initial therapeutic option for protruding and non-protruding condylomata acuminata of the distal urethra

Genital warts (also known as condylomata acuminata) caused by the human papillomavirus (HPV) represent one of the most common sexually transmitted infections. Although they are usually found in the outer genital region, a small proportion of men can present with (often unrecognised) intraurethral warts, generally limited to the distal urethra and urethral meatus. This poses a treatment challenge not adequately addressed by the current guidelines. Here, we present two cases of low-risk HPV-positive patients with protruding and non-protruding condylomata acuminata of the distal urethra, which were treated successfully by using two different topical regimens (ie, a combination of policresulen and imiquimod for one patient and 5-fluorouracil monotherapy for the other). Although this type of management results in lower rates of tissue destruction and complications and may be given preference as an initial therapeutic option, additional prospective comparative clinical studies are needed to elucidate its potential in similar cases.

Diagnostic significance of immunoglobulin G avidity in symptomatic and asymptomatic West Nile virus infection

INTRODUCTION

West Nile virus (WNV) immunoglobulin M (IgM) antibodies have been shown to persist for up to 500 days in certain patients. To evaluate the usefulness of immunoglobulin G (IgG) avidity assessment in the diagnosis of WNV infection, we analyzed 54 WNV IgM- and/or IgG-positive serum samples from 39 patients with neuroinvasive disease and 15 asymptomatic cases tested during a seroprevalence investigation.

METHODS

Serological tests (WNV IgM/IgG antibody detection, IgG avidity) were performed using commercially available enzyme-linked immunosorbent assays.

RESULTS

WNV IgM antibodies were detected in 47 (87%) samples. Acute/recent WNV infection was confirmed based on low/borderline avidity index (AI) in 44 IgM-positive samples (93.6%). In three IgM-positive samples (6.4%), high IgG AIs were detected, thus indicating persisting IgM antibodies from previous infections. All IgM-negative samples showed high AIs. Patients with WNV neuroinvasive disease tested within 30 days showed low AIs. In six patients tested 34-50 days after disease onset, AI was borderline (42%-60%), suggesting earlier WNV IgG maturation. Samples with the highest IgM values were associated with the lowest AIs (Spearman's rho coefficient -0.767, p < 0.001).

CONCLUSIONS

Our results indicate that IgG avidity differentiates current/recent WNV infection from persistent IgM seropositivity from the previous WNV transmission season both in patients with WNV neuroinvasive disease and in asymptomatic persons. A strong negative correlation between IgM antibody levels and AI indicates that in cases with very high IgM levels, determination of IgG avidity may not be necessary. As many patients showed rapid avidity maturation, low IgG avidity is indicative of WNV infection within the previous month.

Dual infection: tularemia and Lyme borreliosis acquired by single tick bite in northwest Croatia

A case of dual infection, tularemia and Lyme borreliosis acquired by a single tick bite in northwest Croatia is presented. The patient came from a highly endemic region for Lyme borreliosis, where 45% of the ticks are infected with Borrelia burgdorferi. Clinically, tularemia manifested as the ulceroglandular form, and Lyme borreliosis manifested with arthritis (knee). Both diseases responded well to combined antibiotic therapy.